EP2425004B1 - Process for producing sugars from lignocellulosic biomass involving a step of alcohol-alkaline delignification in the presence of H2O2 - Google Patents

Description

The present invention relates to a process for the preparation of carbohydrate cleavage products, in particular sugars, such as pentoses and hexoses, from a lignocellulosic material. The invention further relates to a process for the production of alcohol from the sugars. For the purposes of the present specification and claims, the term "sugar" shall also include "sugar oligomers".

In connection with the scarcity of crude oil and the discussion about grain as an energy supplier, the renewable raw material lignocellulose (straw, wood, paper waste, etc.) is gaining in importance as a starting material for fuels or chemical products. Lignocellulose can be converted in two fundamentally different ways: 1) the "Thermochemical Platform", in which the lignocellulose is first gasified and the syngas is synthesized into desired products, and 2) the "Sugar Platform", where the main interest is in the Use of the bound in the polymers cellulose and hemicelluloses sugar, while lignin is still mainly used for energy. The present invention is to be associated with the second route.

In contrast to starch, the sugars of lignocellulose are present in tightly crosslinked, polymeric, crystalline structures of cellulose and hemicelluloses, which are additionally surrounded by a lignin coat, resulting in an extremely dense complex. The most obvious way to extract sugar from lignocellulose would be the direct use of cellulases and hemicellulases. However, this is made more difficult on the raw material straw or wood by the density of the above-mentioned complex. Due to their high molecular weight enzymes are unable to penetrate through the narrow pores in the lignocellulose. This means that a first step must be taken which increases the porosity of the lignocellulose and thereby allows further enzymatic saccharification.

This first step is called "pretreatment". It is very complex throughout, so eg in the production of "second generation biofuels" up to 1/3 of the production costs have to be spent, which has a negative impact on profitability. The applied procedures are aimed either at primarily liquefying the hemicelluloses (eg steam explosion, dilute acid-pretreatment) or at increasing the porosity by liquefying lignin (eg lime, ammonia-pretreatment).

The digested lignocellulose substrate can be treated enzymatically for the recovery of sugars or their oligomers, wherein the type of pretreatment can have a strong influence on the enzyme activity and the yield. At high reaction temperatures, toxic degradation products (eg furfural) often form, which in the case of an immediately connected ethanol fermentation can inhibit the yeasts; see, for. B. Chandra et al., Advances in Biochemical Engineering / Biotechnology, 108: 67, 2007 ; Mansfield et al., Biotechnol. Prog. 15: 804, 1999 ,

These processes have the serious disadvantage that they are energy-consuming and run mainly at temperatures just below 200 ° C.

A technological improvement in this area, e.g. By developing low temperature processes (i.e., at a temperature below 100 ° C), significant progress in any material use of the raw material would be lignocellulose. This is the object of the present invention.

The documents GOULD, JM: "Alkaline Peroxides Delignification of Agricultural Residues to Enhance Enzymatic Saccharification" (BIOTECHNOLOGY AND BIOENGINEERING, Vol. 26, No. 1, 1984, pages 46-52 ) and GOULD, JM & FREER, SN: "High-Efficiency Ethanol Production from Lignocellulosic Residues Pretreated with Alkaline H2O2" (BIOTECHNOLOGY AND BIOENGINEERING, Vol. 26, No. 6, 1984, pages 628-631 disclose processes for the preparation of carbohydrate cleavage products in which lignocellulose-containing material is treated with an aqueous solution containing hydrogen peroxide and a base to oxidatively cleave lignocellulose and separate cleavage products from the material to yield a cellulose-enriched material; the resulting cellulose-enriched material is treated with a carbohydrate-cleaving enzyme to recover the carbohydrate cleavage products.

From the EP 1 025 305 B1 is a chemical process for lignin depolymerization (Cu system) known. It relies on the catalytic action of complexed copper in conjunction with hydrogen peroxide or organic hydroperoxides and is capable of oxidatively cleaving lignin at temperatures below 100 ° C. The complexing agents used are pyridine derivatives. Synthetic lignin models have been shown to cleave ether bonds of the lignin molecule when H ₂ O _{2 is used} as the oxidant, causing the lignin polymer to break down into oligomeric subunits. When using the Cu system with an excess of organic hydroperoxides, it is possible to delignify wood. The H ₂ O ₂ -based system appears to be better technically feasible, was used as a bleach additive in peroxide bleaching of kraft pulp and resulted in an improved delignification rate and higher whiteness.

Furthermore, from " Oxidation of wood and is components in water-organic media ", Chupka et al., Proceedings: Seventh International symposium on wood and pulping chemistry, Vol. 3, 373-382, Beijing PR China, May 25-28, 1993 It is known that the efficiency of alkaline catalysis of the oxidation of wood and lignin increases considerably when an organic solvent, eg DMSO, acetone, ethanol, is added to the aqueous reaction medium. Furthermore, the authors claim that at pH values above 11 there is a sharp increase in the oxidation of wood and lignin.

The patent document US 2004/0163779 A1 discloses a process for bleaching pulp wherein lignocellulose-containing material is treated with an aqueous solution containing hydrogen peroxide, ethanol and a base to oxidatively cleave lignocellulose and separate fission products from the material.

From the WO 01/059204 For example, a process is known for producing pulp in which the starting material is subjected to a pretreatment wherein the material is treated with a buffer solution and a delignification catalyst (transition metal). The delignification is carried out in the presence of oxygen, hydrogen peroxide or ozone.

• lignocellulosisches Material mit einer wässrigen Lösung, welche Wasserstoffperoxid, einen C_1-4-Alkohol und eine Base enthält, behandelt wird, um Lignocellulose oxidativ zu spalten und Spaltprodukte aus dem Material abzutrennen, wobei ein mit Cellulose und Hemicellulose angereichertes Material erhalten wird, und
• das erhaltene, mit Cellulose und Hemicellulose angereicherte Material mit einem Kohlenhydrat-spaltenden Enzym behandelt wird, um die Kohlenhydratspaltprodukte zu gewinnen.

In contrast, the inventive method for producing carbohydrate cleavage products, in particular sugars, characterized in that

• lignocellulosic material is treated with an aqueous solution containing hydrogen peroxide, a C _1-4 alcohol and a base to oxidatively cleave lignocellulose and separate cleavage products from the material to yield a cellulosic and hemicellulose enriched material; and
• the resulting cellulosic and hemicellulose-enriched material is treated with a carbohydrate-cleaving enzyme to recover the carbohydrate cleavage products.

Alcohols which are suitable are aliphatic or cycloaliphatic, mono- or polyhydric C _1-4 -alcohols, such as methanol, ethanol, propanol and butanol, including their isomers; Glycols (ethanediols, propane, butanediols), glycerol, propenol, butenol, but also amino alcohols, such as ethanolamine and methanolamine.

The alcoholic solution of the lignin extract also offers agreeable options in the further processing of the lignin or xylan cleavage products.

Hydrogen peroxide is present in an aqueous alcoholic solution, preferably at a level of from 0.1 to 5% by weight, more preferably at a level of from 0.3 to 2% by weight, for example from 0.3 to 1% by weight.

Alcohol is in an aqueous solution in the inventive method preferably in an amount of 10 to 70 vol%, z. B. 20 to 50 vol%, preferably from 30 to 40 vol% before.

In the process according to the invention, the lignocellulosic material is preferably present in the aqueous solution in a consistency of 3-40% by weight, such as 5-40% by weight, in particular 5-20% by weight.

Preferably, the lignocellulose is at a temperature of below 100 ° C, such as below 80 ° C, z. B. cleaved below 60 ° C.

On the one hand, the present invention is based on the finding that a lignocellulosic material treated with an aqueous basic hydrogen peroxide solution containing one of the above-mentioned C _1-4 alcohols can be enzymatically processed in higher yield into carbohydrate-cleavage products such as sugars otherwise delignified material, in particular without the addition of alcohol.

As carbohydrate cleavage products predominantly sugars, mainly pentoses and hexoses are formed. Preferred sugars include xylose and glucose.

A preferred embodiment of the method according to the invention is characterized in that the cellulosic and hemicellulose-enriched material is treated with a xylanase and a cellulase to recover the sugars.

As lignocellulosic material is preferably straw, energy grasses, such. Switchgrass, elephant grass or abaca, sisal, bagasse or atypical lignocellulosic substrates such as husks, e.g. Rice husks, preferably straw, energy grasses bagasse or husks, particularly preferably straw or bagasse, z. As straw used. Straw has a highly hydrophobic surface, so wetting with aqueous solutions is a problem. It has been found that it is possible by the use of alcohol, even without pressure to introduce the reaction solution into the pores of the substrate and to replace the existing air by reaction solution. It has also been shown that alcohol accelerates the extraction of the cracking products from straw and helps to keep the lignin cleavage products in solution. Furthermore, it has been found that by alcohol the solubility of the hemicellulose and its cleavage products are reduced by alcohol and thus the hemicellulose is kept in the substrate. If metal ions are introduced with the straw, which partially destroy the hydrogen peroxide, then a complexing agent for the metal ions should be added.

A preferred variant of the method according to the invention is that the pH of the aqueous solution prior to the treatment of the lignocellulosic material is less than 12.0, in particular less than 11.0, and greater than 10.0; Further, no base is added during the treatment. This is particularly advantageous for the enzymatic further processing of the sugars to alcohol, since it has been shown that the pH drops during the treatment, so that only a few chemicals to set the optimum pH for the subsequent enzymatic cleavage of carbohydrates and fermentation of Sugar to alcohol are needed.

By pressing off the liquid phase from the substrate after the digestion process, the substrate concentration is increased, so that smaller amounts of enzyme for enzymatic hydrolysis, or in other enzymatic processing are required.

In alcohol production, enzyme costs are a crucial cost factor. Alcohol leads to the fact that the solubility of the hemicelluloses possibly released in the alkaline range during the reaction, in addition to the lignin, and their cleavage products are greatly reduced and these remain bound to the substrate. The advantages for the process are high selectivity of the lignin degradation, in the case of separation of the extraction solution from the solid a very low concentration of hemicellulose and their cleavage products in the extraction solution, because the hemicellulose remains in the solid content and thus obtained for enzymatic hydrolysis and sugar extraction.

The alcoholic solution of the lignin extract also offers improved possibilities in the further processing of the lignin and the production of products from lignin:

The delignification carried out in the digestion increases the porosity of the cell walls of the lignocellulosic material, for example in the case of straw, to such an extent that almost all xylose becomes accessible to the xylanase and approximately 100% of the xylan hydrolyzed and xylose recovered. This makes the process according to the present invention particularly suitable for producing higher-value products in conjunction with an enzymatic conversion of the xylose. The enzymatic conversion can take place either directly in the mixture of xylose solution and solid, or else with the xylose solution separated off from the solid.

In a further, after the enzymatic hydrolysis of the xylan and the inventive conversion of xylose to xylitol following alcohol production from the remaining solid, enzyme costs are a crucial cost factor. These also partly result from unspecific binding of enzymes to the lignin, see, for example, Chandra et al, 2007, ibidem. The partial removal of lignin reduces this loss of activity and has a cost effective.

The advantages for a subsequent enzymatic process are, for example, that from the high selectivity of lignin degradation with almost complete preservation of the sugar polymers a very low concentration of hemicellulose and their cleavage products in the Extraction solution results, the hemicellulose remains in the solid content and thus for the enzymatic hydrolysis and sugar extraction and their further conversion is obtained. This results according to the invention a maximum substance utilization rate and, for example in conjunction with the use of xylose dehydrogenases, high profitability of the process described.

The performance of a xylose conversion process to xylitol can be carried out after enzymatic release of the xylose directly in the solid / liquid mixture obtained according to the present inventive method, which further increases the profitability of the overall process.

In the case of conversion to xylitol, the residual alcohol remaining in the substrate after pressing the solid from the digestion process can be used directly as substrate for the alcohol dehydrogenase for the regeneration of NAD to NADH. If the process is designed to (partially) consume the residual alcohol remaining in the reaction mixture from the digestion, alcohol removal from the product solution becomes (partially) superfluous, further increasing the efficiency of the overall process.

In the case of conversion of the lignin cleavage products, the alcohol acts as a radical scavenger and solvent for cleavage products from enzymatic, biomimetic or chemical depolymerization of the higher molecular weight lignin cleavage products to low molecular weight.

The low proportion of hemicelluose and their cleavage products in the extract and the increased solubility of lignin, increase the throughput rates in a separation of the solid from the conversion products, as well as their processing by filtration.

The inventive method allows, for example, the separation of the three main components of the straw, namely the glucose, xylose and lignin in very low-contaminant streams and their further conversion to higher-value products, such as xylitol, and thus meets the requirements of an ideal biorefinery process.

Another advantage of the method according to the invention in comparison with other digestion processes, which occur predominantly in the temperature range between 1502 ° C and 200 ° C, is that a reaction temperature below 100 ° C can be maintained. The low energy consumption makes it possible to use the lignin obtained during digestion not as an energy source for the digestion process, but as valuable material.

After treatment with the aqueous solution containing a C _1-4 alcohol and H ₂ O ₂ , according to the method of the present invention, the lignin-containing solution is separated and the digested solid is preferably extracted with a xylanase, e.g. B. 6-72 hours at 30-90 ° C and the liquid phase separated from the solid, whereupon the liquid phase is preferred to follow-up products, for. B. xylitol is further reacted.

The remaining after separation of the liquid phase solid is preferably treated with cellulase, which can be obtained by further fermentation of the solid / glucose solution, ethanol, butanol or other fermentation products; or the remaining solid is subjected to a thermal or thermochemical material conversion and the resulting products, such as fuel components, fuel additives and / or other chemical products, such as. As phenols are separated; or the remaining solid is subjected to microbial conversion by bacteria, yeasts or fungi; or the remaining solid is subjected to a further delignification step for the purpose of obtaining a cellulosic fibrous material.

The remaining solid can be fermented in a biogas plant and processed into biogas.

One of the most economically interesting derivatives of xylose is xylitol.

The main sources of xylose recovery are pulping liquors from the pulp industry, which contain a wealth of degradation products, mainly lignin and hemicellulose, so that xylose must first be obtained through laborious separation and purification steps. So describes z. B. H. Harms in "Welcome to the Natural World of Lenzing, world leader in cellulose fiber technology ", autumn conference of the Austrian paper industry, Frantschach (15. 11. 2007 ) the extraction of xylose from the thick liquor by gel filtration, a technically very complex method that is not commonly used for bulk products. The thus obtained xylose is then catalytically converted to xylitol.

In a further aspect, the xylose obtained according to the present invention is fermentation-free converted into xylitol by reaction with a xylose reductase, e.g. B. a xylose dehydrogenase, for example from Candida tenuis, wherein optionally a xylose reductase and optionally a co-substrate for the regeneration of the co-factor and optionally alcohol dehydrogenase and optionally NAD (P) H is added to the xylose solution; in particular, wherein the resulting xylitol is separated by filtration from the lignin cleavage products.

Example 1 and Comparative Example 1A below document the effect of pretreatment in the presence of a C _1-4 alcohol on the yield of reducing sugars after enzymatic hydrolysis.

example 1 Pretreatment of wheat straw

Wheat straw is crushed to a particle size of about 2 cm. 5 g of crushed wheat straw is suspended in a 500 mL reaction vessel in 200 mL of a solution consisting of 49.5% water, 50% ethanol and 0.5% hydrogen peroxide. The suspension is heated to 50 ° C. in a water bath, thermostated and the pH of the suspension is adjusted to a starting pH of 12 using aqueous NaOH solution. The mixture is continuously magnetically stirred at 200 rpm, 60 ° C. for 24 hours. Thereafter, the solid content is filtered off and washed with 1 L of distilled water.

For enzymatic hydrolysis, 100 mg pretreated substrate of each parallel experiment was adjusted to pH 4.8 with 9.8 ml of 50 mM Na acetate buffer and admixed with 200 μl of Accellerase 1000 Suspension (www.genencor.com). Accellerase is an enzyme mixture of cellulases and hemicellulases. The enzymatic hydrolysis was carried out at 50 ° C in a shaking water bath. The soluble monomers of hexoses and pentoses released after 48 hours were reduced in the form of reducing sugars by the DNS method ( Miller et al., Analytical Chemistry 31 (3): 426, 1959 ) in 1 mL of liquid supernatant, based on the amount of weighed, pretreated substrate and expressed in percent of the maximum theoretical yield.

The theoretical maximum yield of reducing sugars was determined separately and is 705 mg +/- 5% per g of untreated straw.

In each case 5 parallel experiments were carried out per test batch. The yield of reducing sugars was 99% +/- 4%.

Comparative Example 1A

Example 1 above was repeated but without the addition of alcohol. The yield of reducing sugars was only 64% +/- 3%.

Example 2 Example 2a Enzymatic xylitol production from a xylose solution made from straw. Isopropanol is used as the co-substrate. The reaction solution contains 5 mg / mL xylose.

Xylose reductase (XR) from Candida tenuis reduces xylose to xylitol. This XR requires as coenzyme NADH (nicotinamide adenine dinucleotide reduced), which is oxidized in the reaction to the coenzyme NAD ⁺ . The regeneration of the oxidized cofactor is carried out by parallel activity of an alcohol dehydrogenase (ADH: enzyme-linked regeneration). Isopropanol is used as the co-substrate. Isopropanol and NAD ⁺ are converted by the ADH to NADH and acetone as shown in Reaction Scheme 1:

• Gesamtvolumen: 1 mL
• Temperatur: 26 ± 2°C
• Magnetrührer: 200 rpm
• Zeit: 15 Stunden
• Zur Deaktivierung der Enzyme wurden alle Proben auf 95°C für 15 Minuten aufgeheizt und als Vorbereitung für die anschließende HPLC-Analyse zentrifugiert.

Table 1 shows the reaction ratios in the 5 different experimental reactions # 049, # 050, # 051, # 052, # 053 and # 054: Table 1 Reaction number # 049 # 050 # 052 # 053 # 054 Substrate batch 1 [μl] 250 250 250 500 500 XR C.tenuis 2 U / mL [μL] 50 50 50 20 mM NADH [μL] 50 50 50 ADH L. kefir 5U / mL [μL] 50 50 Isopropanol [μL] 50 50 50 mM Na-Phosphate buffer, pH 7.0 [μL] 750 650 550 500 300

• Total volume: 1 mL
• Temperature: 26 ± 2 ° C
• Magnetic stirrer: 200 rpm
• Time: 15 hours
• To deactivate the enzymes, all samples were heated to 95 ° C for 15 minutes and centrifuged in preparation for subsequent HPLC analysis.

Analysis - HPLC:

• Column SUGAR SP0810 + Pre-column SUGAR SP-G
• Detector: refractive index detector
• Eluent: deionized H ₂ O
• Flow: 0.75 mL / min
• Sample amount: 10 μL
• HPLC quantification precision: ± 10%

Retention time:

• Xylose: 13.97 min
• Xylitol: 37.73 min
• Isopropanol: 16.69 min
• Acetone: 16.54 min

Results:

The substrate concentration of sample # 049 was determined by HPLC to be 0.9 mg / mL.

Reaction Mixture # 050 contains only xylose reductase (0.1 U / mL) and NADH (1 mM). After the 15 hour reaction, 0.085 mg of xylose was consumed. The xylitol concentration was below the detection limit.

Reaction # 052 is similar to Reaction # 050 except that the regeneration system is used here. It comes to the total sales of the used xylose. Concentrations used: XR (0.1 U / mL), NADH (1 mM), ADH (0.25 U / mL) and isopropanol (5%).

The xylose concentration of sample # 053 was determined to be 2.121 mg / mL, which corresponds to the expected xylose concentration.

Reaction # 054 is similar to Reaction # 052, but involves a factor of 2 increased xylose start concentration (50% substrates in the reaction). The concentration of xylitol produced was measured with 0.945 mg of xylitol. Concentrations used: XR (0.1 U / mL), NADH (1 mM), ADH (0.25 U / mL) and isopropanol (5%).

In Table 2, the results of the reactions are summarized based on the HPLC measurement data (xylose consumed and xylitol recovered; uDL means "below the detection limit"): Table 2 response number 049 050 052 053 054 Xylose before the reaction [mg / mL] 0.9 0,815 0.8 2,121 1,945 Xylose after the reaction [mg / mL] - 0,815 UDL - 1.013 Xylose consumed in the reaction [mg / mL] - UDL - 0.932 Extraction of xylitol [mg / mL] - UDL 0.994 - 0.945 Xylitol yield relative to xylose concentration [%] - UDL 100 - 47.9

Example 2b Enzymatic xylitol production from a xylose solution made from straw. The cosubstrate used is ethanol.

The volume of the substrate solution was reduced to 50% (see Example 2) using a rotavapor to increase the xylose concentration (~10 mg / mL xylose).

The regeneration of the oxidized cofactor was carried out by the activity of the candida tenius xylose reductase (XR) used and the additional activity of an aldehyde dehydrogenase from Saccharomyces cerevisiae used (Sigma-Aldrich: catalog number A6338; (EC) Number: 1.2.1.5; CAS Number: 9028-88-0). This is both a substrate-coupled, as well as an enzyme-coupled reaction. The cosubstrate used is ethanol. Ethanol and NAD ⁺ are converted in the first step by the activity of the XR to NADH and acetaldehyde. In the second step, acetaldehyde and NAD ^{+ are} converted to acetate by the activity of aldehyde dehydrogenase (AldDH) (see Sigma-Aldrich: catalog number A6338; Characterization and Potential Roles of Cytosolic and Mitochondrial Aldehyde Dehydrogenases in Ethanol Metabolism in Saccharomyces cerevisiae ", Wang et al, Molecular Cloning, 1998, Journal of Bacteriology, pp. 822-830 ). In this case, 2 mol of reduction equivalents (NADH) would be formed per mole of co-substrate converted (compare Reaction Scheme 2).

Table 3 shows the reaction conditions of the 4 different reaction reactions 247, 249, 250 and 253. Different ethanol concentrations and AldDH concentrations were used. The cofactor and substrate concentrations were kept constant.

• Gesamtvolumen: 0,5 mL
• Temperatur: 25 ± 2°C
• Thermomixer: 500 rpm
• Zeit 112 Stunden

Table 3 response number 247 249 250 253 Substrate batch III [μL] 300 (56 mM) 300 (56 mM) 300 (56 mM) 300 (56 mM) XR C. tenius 5U / mL [μL] 25 (0.25 U / mL) 25 (0.25 U / mL) 25 (0.25 U / mL) 25 (0.25 U / mL) 20 mM NAD ⁺ [μL] 10 (0.4 mM) 10 (0.4 mM) 10 (0.4 mM) 10 (0.4 mM) AldDH S. cervisiae 5U / mL [μL] 25 (0.25U / mL 25 (0.25U / mL) 0 0 Ethanol 50% [μL] 75 (1286 mM) 70 (1200 mM) 75 (1286 mM) 70 (1200 mM) 50 mM TrisHCl buffer pH 7.0 [μL] 65 70 90 95

• Total volume: 0.5 mL
• Temperature: 25 ± 2 ° C
• Thermomixer: 500 rpm
• Time 112 hours

To deactivate the enzymes, all samples were heated to 70 ° C for 15 minutes and centrifuged and filtered (PVDF, 0.2 μm) in preparation for subsequent HPLC analysis.

Analysis - HPLC:

• Column SUGAR SP0810 + Pre-column SUGAR SP-G
• Column temperature: 90 ° C
• Detector: refractive index detector
• Eluent: deionized H ₂ O
• Flow: 0.90 mL / min
• Sample amount: 10 μL
• HPLC quantification precision: ± 10%

Results:

The maximum yield (reaction 249) could be achieved with an ethanol concentration of 1.2 mol / L. A total of 1.38 mg / mL xylitol was produced, which corresponds to a yield of 21.2% of theory of xylitol.

Table 4 summarizes the results of the reactions based on the HPLC measurement data. Table 4 response number 247 249 250 253 Theoretical total concentration [mg / mL] 6,288 6,407 6,268 6,150 Xylose after the reaction [mg / mL] 5,057 5,046 5,385 5,365 Xylose consumed in the reaction [mg / mL] 1,231 1,361 0.883 0,785 Extraction of xylitol [mg / mL] 1,248 1,379 0.894 0796

From the results, it can be seen that ethanol can be used as a cosubstrate. As can be clearly shown by comparing the reaction 249 (reaction mixture includes AldDH) and 253 (reaction mixture without AldDH), the addition of the aldehyde dehydrogenase leads to a marked increase in the yield of xylitol. The difference in converted xylose to xylitol is ~ 8%. This result, in conjunction with the above-mentioned references, only allows the conclusion that AldDH further oxidizes the acetaldehyde formed in the first partial reduction to acetic acid (compare Reaction Scheme 2). This energetically favorable reaction and the concomitant increased concentration of NADH shifts the equilibrium of the educt towards the product xylitol in the first partial reaction.

Claims (13)

1. A method for the production of carbohydrate cleavage products, characterized by the combination of the measures that

   - lignocellulosic material is treated with an aqueous solution containing hydrogen peroxide, an C_1-4 alcohol and a base, in order to oxidatively break down lignocellulose and to separate cleavage products from the material, wherein there is obtained a material enriched with cellulose and hemicellulose, and

   - the obtained material enriched with cellulose and hemicellulose is treated with a carbohydrate-cleaving enzyme, in order to prepare carbohydrate cleavage products.
2. A method according to claim 1, wherein the carbohydrate cleavage products are sugars.
3. A method according to any one of claims 1 or 2, characterized in that the cleavage is carried out at a temperature below 100°C.
4. A method according to any one of claims 1 to 3, characterized in that the aqueous solution before the treatment of the lignocellulosic material has a pH that is larger than 10.0 and less than 12.0.
5. A method according to claim 4, wherein the pH is larger than 10.0 and less than 11.0.
6. A method according to claim 4, characterized in that there is not added any base during the treatment.
7. A method according to any of claims 1 to 6, characterized in that there is used as lignocellulosic material straw, bagasse, energy crops and/or bran.
8. A method according to any of claims 1 to 7, characterized in that the lignocellulosic material is present in the aqueous solution in a material density of 5-40 % by weight.
9. A method according to any of claims 1 to 8, characterized in that the material enriched with cellulose and hemicellulose is treated with a xylanase and/or cellulose in order to prepare the sugars.
10. A method according to any one of claims 1 to 9, characterized in that the prepared sugars are fermented to alcohol which is separated and yielded.
11. A method according to any of claims 1 to 10, characterized in that the solid pulped upon the treatment is converted with a xylanase and that the obtained liquid phase is converted into xylitol, and the remaining solid

    - is further converted with cellulase to obtain various fermentation products; or

    - is subjected to a thermal or thermochemical conversion reaction; or

    - is subjected to a microbial conversion by means of bacteria, yeast or fungi; or

    - is subjected to a further delignification step for the purpose of the preparation of a cellulose fibre material.
12. A method according to claim 11, characterized in that the solid pulped upon the treatment is converted with a xylanase and the liquid phase obtained is converted into xylitol using a xylose dehydrogenase, and the remaining solid

    - is further converted with cellulase to prepare various fermentation products; or

    - is subjected to a thermal or thermochemical conversion reaction; or

    - is subjected to a microbial material conversion by means of bacteria, yeast or fungi; or

    - is subjected to a further delignification step for the purpose of the preparation of a cellulose fibre material.
13. A method according to any one of claims 11 or 12, characterized in that the solid remaining upon the separation of the (fermentation) products is fermented in a biogas plant and further processed into biogas.